CN116520173A

CN116520173A - Method for measuring self-discharge rate of battery

Info

Publication number: CN116520173A
Application number: CN202310509458.9A
Authority: CN
Inventors: 朱琳; 蒋治亿; 杨娜伟
Original assignee: Trina Energy Storage Solutions Jiangsu Co Ltd
Current assignee: Trina Energy Storage Solutions Jiangsu Co Ltd
Priority date: 2023-05-08
Filing date: 2023-05-08
Publication date: 2023-08-01

Abstract

The application provides a measurement method of a battery self-discharge rate, which comprises the following steps: acquiring dOCV/dQ of a battery to be tested corresponding to a target SOC; charging the battery to be tested to a target SOC (state of charge) to obtain the battery to be tested of the target SOC; acquiring self-discharge current of a target SOC battery to be tested; and calculating the self-discharge rate of the battery to be tested corresponding to the target SOC according to the dOCV/dQ and the self-discharge current. According to the measuring method, the self-discharge rate of the battery to be measured under the target SOC is calculated according to the dOCV/dQ and the self-discharge current corresponding to the target SOC, and compared with the method for obtaining the voltage drop of the open-circuit voltage of the battery to be measured, the method for obtaining the self-discharge current of the battery to be measured is short in time length, and therefore measuring efficiency is improved. In addition, since the standing time required for obtaining the self-discharge current is short, the self-discharge rate of the self-discharge current measuring device is less influenced by environmental change and precision of a measuring instrument in the standing process, and accuracy of a measuring result is improved.

Description

Method for measuring self-discharge rate of battery

Technical Field

The application mainly relates to the technical field of batteries, in particular to a method for measuring a self-discharge rate of a battery.

Background

The lithium ion battery is widely applied to industries such as digital electronic products, power energy sources and the like because of the advantages of high energy density, long sequential service life, no memory effect and the like. The phenomenon of spontaneous loss of capacity when a lithium ion battery is in an open rest state is called self-discharge of the lithium ion battery, and may also be called charge retention capacity of the lithium ion battery. The self-discharge measurement method mainly comprises the following steps: capacitance measurement, open-circuit voltage measurement, and current measurement. Among them, an open-circuit voltage measurement method (also referred to as a K-value measurement method) is widely used, which measures the self-discharge rate of a battery by measuring the voltage drop of the battery in a unit time. However, the open-circuit voltage measurement method needs to stand the battery to be measured for a long time, so that the period of the open-circuit voltage measurement method is long; in addition, factors influencing the accuracy of the measurement result of the open circuit voltage measurement method are many, such as depolarization effect of the battery, ambient temperature of rest, time of rest and accuracy of the measuring instrument, so the accuracy of the measurement result of the open circuit voltage measurement method is low.

Therefore, how to rapidly and accurately measure the self-discharge rate of a lithium battery is a problem to be solved.

Disclosure of Invention

The technical problem to be solved by the application is to provide a method for measuring the self-discharge rate of a battery, which can rapidly and accurately measure the self-discharge rate of a lithium battery.

The technical scheme adopted for solving the technical problems is a method for measuring the self-discharge rate of a battery, comprising the following steps: acquiring dOCV/dQ of a battery to be tested corresponding to a target SOC; charging the battery to be tested to a target SOC to obtain the battery to be tested of the target SOC; acquiring the self-discharge current of the target SOC battery to be tested; and calculating the self-discharge rate of the battery to be tested corresponding to the target SOC according to the dOCV/dQ and the self-discharge current.

In an embodiment of the present application, a method for obtaining a dOCV/dQ of a battery to be tested corresponding to a target SOC includes: acquiring the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested; calculating equivalent dOCV/dQ according to the corresponding relation between the equivalent OCV and the equivalent Q; and acquiring the dOCV/dQ of the battery to be tested corresponding to the target SOC according to the corresponding relation between the equivalent dOCV/dQ and the equivalent SOC.

In an embodiment of the present application, a method for obtaining a correspondence between an equivalent OCV, an equivalent Q, and an equivalent SOC of an equivalent battery to be measured includes: charging the equivalent battery to be detected according to a preset charging condition to obtain the equivalent battery to be detected in a full-charge state; and discharging the equivalent battery to be tested in the full-charge state according to a preset discharging condition to obtain the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested.

In an embodiment of the present application, the preset charging condition is: and charging the equivalent battery to be tested to a first cut-off voltage by using a constant charging current, and then charging the equivalent battery to be tested to a full-charge state by using the first cut-off voltage as a charging voltage.

In an embodiment of the present application, the preset discharge condition is: and discharging the equivalent battery to be tested in the full-charge state to a second cut-off voltage by using a constant discharge current.

In an embodiment of the present application, the self-discharge current of the target SOC battery to be measured under a preset condition is obtained after the target SOC battery to be measured is subjected to a standing process.

In an embodiment of the present application, the duration of the standing treatment is 12h to 24h.

In one embodiment of the present application, the temperature of the preset condition is 20 ℃ to 30 ℃.

In an embodiment of the present application, the self-discharge current is obtained when the target SOC battery to be measured is in a stable self-discharge state.

In an embodiment of the present application, a formula for calculating the self-discharge rate of the battery to be tested corresponding to the target SOC according to the dcv/dQ and the self-discharge current is as follows: k= (dcv/dQ) ×i, where K represents a self-discharge rate of the battery to be tested corresponding to the target SOC, and I represents the self-discharge current.

According to the measuring method, the battery self-discharge rate is calculated according to the dOCV/dQ and the self-discharge current corresponding to the target SOC, the voltage drop of the open-circuit voltage of the battery to be measured does not need to be obtained, instead, the self-discharge current of the battery to be measured is obtained, and compared with the voltage drop of the open-circuit voltage of the battery to be measured, the time required for obtaining the self-discharge current of the battery to be measured is shorter, so that the measuring efficiency is improved. In addition, because the standing time required for obtaining the self-discharge current is short, the self-discharge rate is less influenced by environmental change and the precision of a measuring instrument in the standing process, and thus the accuracy of a measuring result is improved.

Drawings

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below, wherein:

FIG. 1 is an exemplary flow chart of a method of measuring a self-discharge rate of a battery according to an embodiment of the present application;

FIG. 2 is a graph of OCV-SOC during self-discharge of a battery according to one embodiment of the present application;

FIG. 3 is a plot of dOCV/dQ-SOC during self-discharge of a battery in accordance with one embodiment of the present application.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced otherwise than as described herein, and therefore the present application is not limited to the specific embodiments disclosed below.

As used in this application and in the claims, the terms "a," "an," "the," and/or "the" are not specific to the singular, but may include the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that the steps and elements are explicitly identified, and they do not constitute an exclusive list, as other steps or elements may be included in a method or apparatus.

In addition, the terms "first", "second", etc. are used to define the components, and are merely for convenience of distinguishing the corresponding components, and unless otherwise stated, the terms have no special meaning, and thus should not be construed as limiting the scope of the present application. Furthermore, although terms used in the present application are selected from publicly known and commonly used terms, some terms mentioned in the specification of the present application may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Furthermore, it is required that the present application be understood, not simply by the actual terms used but by the meaning of each term lying within.

Flowcharts are used in this application to describe the operations performed by systems according to embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in order precisely. Rather, the various steps may be processed in reverse order or simultaneously. At the same time, other operations are added to or removed from these processes.

The measuring method of the present application will be described below by way of specific examples.

Fig. 1 is an exemplary flowchart of a method of measuring a battery self-discharge rate according to an embodiment. Referring to fig. 1, the measurement method of this embodiment includes the steps of:

step S110: acquiring dOCV/dQ of a battery to be tested corresponding to a target SOC;

step S120: charging the battery to be tested to a target SOC (state of charge) to obtain the battery to be tested of the target SOC;

step S130: acquiring self-discharge current of a target SOC battery to be tested;

step S140: and calculating the self-discharge rate of the battery to be tested corresponding to the target SOC according to dock/dQ and the self-discharge current.

Where SOC represents the State of Charge (State of Charge) of the battery, OCV represents the open circuit voltage (Open Circuit Voltage) of the battery, Q represents the discharge capacity of the battery, and diocv/dQ represents the differentiation of the open circuit voltage to the discharge capacity.

The following specifically describes the steps S110 to S140 described above.

In step S110, the method for obtaining the dcv/dQ of the battery to be tested corresponding to the target SOC includes:

step S111: acquiring the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested;

step S112: calculating equivalent dOCV/dQ according to the corresponding relation between the equivalent OCV and the equivalent Q;

step S113: and acquiring the dOCV/dQ of the battery to be tested corresponding to the target SOC according to the corresponding relation between the equivalent dOCV/dQ and the equivalent SOC.

The specification parameters of the equivalent battery to be measured in step S111 to step S113 are the same as those of the battery to be measured, and the electrical properties of the equivalent battery to be measured are the same or substantially the same as those of the battery to be measured, so that the electrical parameters (for example, equivalent dcv/dQ, equivalent SOC, and correspondence relationship therebetween) of the equivalent battery to be measured may be used to represent the electrical parameters (dcv/dQ corresponding to the target SOC) of the battery to be measured. Therefore, when the number of the batteries to be measured is large, the electrical parameters of the batteries to be measured are compared with the electrical parameters obtained one by one, and the electrical parameters of the batteries to be measured are represented by the electrical parameters of the equivalent batteries to be measured, so that the time for obtaining the electrical parameters of the batteries to be measured can be shortened. Note that, the method of acquiring the dcv/dQ of the battery to be measured corresponding to the target SOC in the present application is not limited to steps S111 to S113. In some embodiments, the dcv/dQ of the battery under test corresponding to the target SOC may also be obtained based on the electricity under test, for example, steps S111 to S113 may be performed based on the battery under test. The battery to be tested comprises a ternary lithium battery and a lithium iron phosphate battery.

Next, step S111 to step S113 will be described by way of example.

In step S111, a plurality of equivalent batteries to be measured are taken, and the plurality of equivalent batteries to be measured are charged according to a preset charging condition, so as to obtain the equivalent batteries to be measured in a full-charge state. The number of the equivalent batteries to be measured is not limited, and the equivalent batteries to be measured can be one or any natural number larger than 1. When the number of the equivalent batteries to be measured is plural, the average value of the electrical parameters of the plurality of the equivalent batteries to be measured can be used for representing the electrical parameters of the batteries to be measured.

In one embodiment, the preset charging conditions are: the equivalent battery to be measured is charged to the cut-off voltage OCV1 by the constant charging current I1, and then the equivalent battery to be measured is charged to the full-charge state by taking the cut-off voltage OCV1 as the charging voltage. In some embodiments, during charging of the equivalent battery under test with the cutoff voltage OCV1, the charging current is detected, and when the charging current drops to the cutoff current I2, the charging of the equivalent battery under test is stopped. The cut-off current I2 represents the charging current of the equivalent battery to be tested in a full-charge state; in other words, it is possible to determine whether the equivalent battery to be measured is in a full state by detecting the current in the charging process of the equivalent battery to be measured. It should be understood that "full state" does not refer to a strictly full state, and includes an approximately full state, such as when the battery is at 98% soc, which may also be considered to be in a full state. In some embodiments, the charging current I1 may be any value from 0.3C to 0.5C, the specific value of OCV1 being related to the type of equivalent battery to be tested, for example, when the equivalent battery to be tested is a ternary lithium battery, OCV1 may be 4.2V; when the equivalent battery to be measured is a lithium iron phosphate battery, OCV1 may be 3.65V.

And discharging the equivalent battery to be tested in the full-charge state according to a preset discharging condition to obtain the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested.

In the discharging process of the equivalent battery to be tested, the SOC, the Q and the OCV of the equivalent battery to be tested are changed along with the discharging process, and the corresponding relation exists among the SOC, the Q and the OCV. In order to distinguish from the SOC, Q, and OCV of the battery to be measured, the SOC, Q, and OCV of the equivalent battery to be measured are referred to as equivalent OCV, equivalent Q, and equivalent SOC, respectively. In the discharging process, the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested and the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC are recorded. For convenience of description, the correspondence between the equivalent OCV and the equivalent SOC will be referred to as (equivalent OCV, equivalent SOC).

In some embodiments, the preset discharge conditions are: and discharging the equivalent battery to be tested in the full-charge state to the cut-off voltage OCV2 by using the constant discharge current I3. The application does not limit the discharge current I3 and the cut-off voltage OCV2, and can set specific discharge current I3 and cut-off voltage OCV2 according to the specification parameters and measurement requirements of the battery. In some embodiments, the discharge current I3 may be 0.02C, the specific value of the cut-off voltage OCV2 is related to the type of equivalent battery to be tested, for example, when the equivalent battery to be tested is a ternary lithium battery, OCV2 may be 2.75V; when the equivalent battery to be measured is a lithium iron phosphate battery, OCV2 may be 2.5V.

As described above, there is a correspondence relationship among the equivalent OCV, the equivalent Q, and the equivalent SOC. Fig. 2 is an OCV-SOC curve during self-discharge of a battery according to an embodiment, wherein an abscissa may represent an equivalent SOC of an equivalent battery to be measured and an ordinate may represent an equivalent OCV of the equivalent battery to be measured. The OCV-SOC curve shown in fig. 2 may be plotted according to the correspondence between the equivalent OCV and the equivalent SOC. There is also a similar OCV-Q curve between the equivalent OCV and the equivalent Q, which is not developed here.

In step S112, an equivalent dcv/dQ is calculated from the correspondence between the equivalent OCV and the equivalent Q acquired in step S111. In some embodiments, the equivalent dOCV/dQ may be calculated by deriving the equivalent OCV from the equivalent Q.

There is a correspondence between the equivalent dOCV/dQ and the equivalent OCV, i.e., each equivalent OCV has an equivalent dOCV/dQ corresponding thereto. For convenience of description, the correspondence between equivalent dOCV/dQ and equivalent OCV is referred to as (equivalent dOCV/dQ, equivalent OCV). The correspondence between the equivalent dOCV/dQ and the equivalent SOC can be obtained by combining the equivalent dOCV/dQ and the equivalent OCV (equivalent SOC), and is expressed as (equivalent SOC, equivalent dOCV/dQ). FIG. 3 is a plot of dOCV/dQ-SOC during battery self-discharge of an embodiment, wherein the abscissa represents equivalent SOC and the ordinate represents equivalent dOCV/dQ. The dOCV/dQ-SOC curves shown in FIG. 3 may be plotted against (equivalent SOC, equivalent dOCV/dQ).

In step S113, the dcv/dQ of the battery to be measured corresponding to the target SOC is obtained from the (equivalent SOC, equivalent dcv/dQ) in step S112. As described above, the electrical parameters of the battery to be measured may be represented using the electrical parameters of the equivalent battery to be measured. Therefore, the corresponding dcv/dQ of the target SOC in the battery to be measured can be obtained according to the correspondence between the equivalent SOC and the equivalent dcv/dQ (i.e., equivalent SOC, equivalent dcv/dQ), and for convenience of description, the target SOC and the corresponding dcv/dQ in the battery to be measured are expressed as (target SOC, dcv/dQ).

The method of obtaining (target SOC, dOCV/dQ) based on (equivalent SOC, equivalent dOCV/dQ) includes look-up table and querying dOCV/dQ-SOC curve. For example, referring to FIG. 3, the curve in FIG. 3 shows the correspondence between equivalent SOCs and equivalent dOCVs/dQs, i.e., each equivalent SOCs has an equivalent dOCV/dQ corresponding thereto. Assuming that the target SOC is 5% SOC, the equivalent dOCV/dQ is 20 when the equivalent SOC is 5% SOC can be obtained by looking up FIG. 3, and therefore the dOCV/dQ of the battery to be tested corresponding to 5% SOC is 20.

In step S120, the battery to be measured is charged to the target SOC to obtain the target SOC battery to be measured. The description of step S120 will be continued with the above example. Assuming that the target SOC is 5% SOC, the battery to be tested is charged to 5% SOC to obtain the battery to be tested with 5% SOC.

In one embodiment, the process of charging the battery under test to 5% soc is as follows: firstly, charging a battery to be tested in a constant current charging mode, wherein the charging current is I4, and the cut-off voltage is OCV3; then, the battery to be tested is charged by adopting a constant voltage charging mode, the charging voltage is OCV3, and the cut-off current is I5. An equivalent OCV corresponding to 5% SOC can be obtained from (equivalent OCV, equivalent SOC), and this equivalent OCV is taken as the cut-off voltage OCV3. And obtaining the battery to be tested with 5% SOC through the charging process. It should be noted that, the method for obtaining the target SOC battery to be measured is not limited to the above-described process.

In step S130, the target SOC battery to be measured obtained in step S120 is self-discharged to obtain a self-discharge current of the target SOC battery to be measured.

In an embodiment, a method for obtaining a self-discharge current of a battery to be tested of a target SOC includes: standing the battery to be tested of the target SOC; and obtaining the self-discharge current of the target SOC battery to be tested under the preset condition. Wherein, the time of the standing treatment can be any time in 12-24 hours; the preset conditions include humidity and/or temperature of the standing treatment, and the temperature can be any temperature of 20-30 ℃. After the battery is charged, the battery is relatively active, and the standing treatment is helpful for balancing lithium ions in the battery to be measured of the target SOC.

In some embodiments, the target SOC battery under test may be placed in a constant temperature room, and the self-discharge current of the target SOC battery under test may be obtained using a self-discharge tester. In other embodiments, the self-discharge current is obtained when the target SOC battery to be measured is in a stable self-discharge state, and the self-discharge current in the stable self-discharge state can more accurately reflect the self-discharge characteristics of the target SOC battery to be measured.

In the conventional technology, when the self-discharge rate of the battery is obtained by using an open-circuit voltage measurement method, the battery to be measured needs to be stood for a long time to obtain the voltage drop of the open-circuit voltage of the battery to be measured within the standing time. According to the method and the device, the voltage drop of the open-circuit voltage of the battery to be measured is not required to be obtained, instead, the self-discharge current of the battery to be measured is obtained, and compared with the voltage drop of the open-circuit voltage of the battery to be measured, the time required for obtaining the self-discharge current of the battery to be measured is shorter, so that the efficiency of measuring the self-discharge rate of the battery is improved.

In addition, because the standing time required for obtaining the self-discharge current is short, the self-discharge rate is less influenced by environmental change and the precision of a measuring instrument in the standing process, and thus the accuracy of a measuring result is improved.

In step S140, the self-discharge rate of the battery to be measured corresponding to the target SOC is calculated from the dcv/dQ and the self-discharge current. The description of step S140 continues with the previous example. In the foregoing example, the target SOC is 5% SOC, and the diocv/dQ corresponding to 5% SOC is found to be 20 in step S110; assuming that the self-discharge current of the 5% SOC battery to be tested is I6; calculating the self-discharge rate of the battery to be tested corresponding to 5% SOC according to dOCV/dQ=20 and 5% SOC

In one embodiment, the formula for calculating the self-discharge rate of the battery to be measured corresponding to the target SOC according to dOCV/dQ and the self-discharge current is as follows: k= (dcv/dQ) ×i, where K represents the self-discharge rate of the battery to be measured corresponding to the target SOC, and I represents the self-discharge current. In connection with the above example, the dcv/dq=20 and the self-discharge current I6 are calculated into the above formula: at 5% soc, the self-discharge rate k=20×i6 of the battery to be measured. The value of the target SOC may be set according to the need, and the target SOC is not limited to the 5% SOC in the foregoing, and for example, the target SOC may be any one of 10% SOC, 20% SOC, 30% SOC, 40% SOC, 50% SOC, 60% SOC, 70% SOC, 80% SOC, 90% SOC, and 100% SOC.

In the conventional technology, when the self-discharge rate of the battery is obtained by using an open-circuit voltage measurement method, the battery to be measured needs to be stood for a long time to obtain the voltage drop of the open-circuit voltage of the battery to be measured within the standing time. According to the measuring method for calculating the self-discharge rate of the battery according to the dOCV/dQ and the self-discharge current corresponding to the target SOC, the battery does not need to be kept stand for a long time, and the duration for measuring the self-discharge rate of the battery is shortened.

For a clearer understanding of the measurement method of the present application, a specific example is given here. This embodiment comprises the steps of:

step 1: taking a lithium iron phosphate battery as an equivalent battery to be measured, and carrying out constant-current charging on the equivalent battery to be measured, wherein the charging current is 0.3C, and the cut-off voltage is 3.65V; then, the equivalent battery to be measured is charged with a constant voltage of 3.65V, and the cut-off current is 0.02C.

Step 2: discharging the equivalent battery to be tested, wherein the discharging current is 0.02C, and the cut-off voltage is 2.5V; and recording the OCV and Q of the equivalent battery to be tested in the discharging process and the corresponding relation between the SOC and the OCV of the equivalent battery to be tested. An OCV-SOC curve as shown in fig. 2 may be plotted according to the correspondence between the equivalent battery SOC to be measured and the OCV.

Table 1 is a self-discharge rate calculation table, and OCV during discharge of the equivalent battery to be measured is recorded in table 1.

Step 3: deriving the OCV pair Q to obtain dOCV/dQ corresponding to different OCVs; dOCV/dQ corresponding to different SOCs is obtained from the correspondence between SOCs and OCVs represented by the curves in FIG. 1. A curve as shown in fig. 3 may be plotted according to the correspondence between SOC and dcv/dQ.

Step 4: taking 30 batteries to be tested, equally dividing the batteries into 10 groups, and sequentially numbering the groups as 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9# and 10#, wherein the target SOCs of the batteries to be tested in each group are respectively as follows: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% SOC; and (3) respectively adjusting the SOC of the 1# to 10# groups of batteries to be tested to respective target SOCs. The adjusting flow is as follows: constant current charging is carried out firstly, the charging current is 0.3C, and the cut-off voltage is obtained from the graph 2; then constant voltage charging is carried out, and the cut-off current is 0.02C; and standing the 1# to 10# batteries to be tested at normal temperature for 24 hours.

And acquiring dOCV/dQ corresponding to the target SOC according to the data in FIG. 3 or steps 1 to 3. For example, the equivalent battery to be tested may be queried for the dcv/dQ corresponding to each target SOC through fig. 3, and the queried dcv/dQ is recorded in table 1, where there is a correspondence between the target SOCs and the dcv/dQ located in the same row.

Step 5: placing 1# to 10# groups of batteries to be tested in a constant temperature room, wherein the temperature of the constant temperature room is controlled to be 25+/-1 ℃; detecting the self-discharge current of each battery to be detected by using a self-discharge tester, and recording the self-discharge current value when the current is stable; the average self-discharge current of each group of cells to be tested was calculated and the calculation result was recorded in table 1.

Step 6: the self-discharge rate K of each group of batteries was calculated according to the formula k= (dcv/dQ) ×i, and the calculation result is shown in table 1, where there is a correspondence between the self-discharge rate of the same row and the target SOC, for example, the target SOC of the 4# group of batteries to be measured is 70%, and the corresponding self-discharge rate K is 0.02100.

TABLE 1 self-discharge Rate calculation Table

Numbering device	OCV(mV)	Target SOC	dOCV/dQ(mV/mAh)	Self-discharge current (mA)	K(mV/h)
						1#	3561.05	100％	1.0320135	64	66.04886
2#	3319.8	90％	0.0002221	59	0.01310
						3#	3316.64	80％	0.0002667	52	0.01387
4#	3311.81	70％	0.0005123	41	0.02100
						5#	3282.01	60％	0.0008941	35	0.03129
6#	3275.54	50％	0.0001992	28	0.00558
						7#	3272.01	40％	0.0003444	25	0.00861
8#	3257.43	30％	0.0016531	21	0.03472
						9#	3223.91	20％	0.0029789	16	0.04766
10#	3181.08	10％	0.0010534	12	0.01264

While the basic concepts have been described above, it will be apparent to those skilled in the art that the foregoing application disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations of the present application may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this application, and are therefore within the spirit and scope of the exemplary embodiments of this application.

Meanwhile, the present application uses specific words to describe embodiments of the present application. Reference to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic is associated with at least one embodiment of the present application. Thus, it should be emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various positions in this specification are not necessarily referring to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present application may be combined as suitable.

In some embodiments, numbers describing the components, number of attributes are used, it being understood that such numbers being used in the description of embodiments are modified in some examples by the modifier "about," approximately, "or" substantially. Unless otherwise indicated, "about," "approximately," or "substantially" indicate that the number allows for a 20% variation. Accordingly, in some embodiments, numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and employ a method for preserving the general number of digits. Although the numerical ranges and parameters set forth herein are approximations that may be employed in some embodiments to confirm the breadth of the range, in particular embodiments, the setting of such numerical values is as precise as possible.

Claims

1. A method for measuring a self-discharge rate of a battery, comprising:

acquiring dOCV/dQ of a battery to be tested corresponding to a target SOC;

charging the battery to be tested to a target SOC to obtain the battery to be tested of the target SOC;

acquiring the self-discharge current of the target SOC battery to be tested; and

and calculating the self-discharge rate of the battery to be tested corresponding to the target SOC according to the dOCV/dQ and the self-discharge current.

2. The measurement method according to claim 1, wherein the method of acquiring the dcv/dQ of the battery to be measured corresponding to the target SOC includes:

acquiring the corresponding relation among the equivalent OCV, the equivalent Q and the equivalent SOC of the equivalent battery to be tested;

calculating equivalent dOCV/dQ according to the corresponding relation between the equivalent OCV and the equivalent Q;

and acquiring the dOCV/dQ of the battery to be tested corresponding to the target SOC according to the corresponding relation between the equivalent dOCV/dQ and the equivalent SOC.

3. The measurement method according to claim 2, wherein the method of obtaining the correspondence between the equivalent OCV, the equivalent Q, and the equivalent SOC of the equivalent battery to be measured includes:

charging the equivalent battery to be detected according to a preset charging condition to obtain the equivalent battery to be detected in a full-charge state;

4. A measurement method according to claim 3, wherein the preset charging conditions are: and charging the equivalent battery to be tested to a first cut-off voltage by using a constant charging current, and then charging the equivalent battery to be tested to a full-charge state by using the first cut-off voltage as a charging voltage.

5. A measurement method according to claim 3, wherein the predetermined discharge condition is: and discharging the equivalent battery to be tested in the full-charge state to a second cut-off voltage by using a constant discharge current.

6. The measurement method according to claim 1, wherein the self-discharge current of the target SOC battery under preset conditions is obtained after the stationary treatment of the target SOC battery.

7. The method according to claim 6, wherein the time period of the standing treatment is 12 to 24 hours.

8. The method according to claim 6, wherein the temperature of the preset condition is 20 ℃ to 30 ℃.

9. The measurement method according to claim 6, wherein the self-discharge current is obtained when the target SOC battery to be measured is in a stable self-discharge state.

10. The measurement method according to claim 1, wherein a formula for calculating a self-discharge rate of the battery to be measured corresponding to the target SOC from the dcv/dQ and the self-discharge current is: k= (dcv/dQ) ×i, where K represents a self-discharge rate of the battery to be tested corresponding to the target SOC, and I represents the self-discharge current.